(1) Field of the Invention
The present invention relates to an amino-carboxylic acid chelating agent excellent in biodegradability and to the uses of the chelating agent. More particularly, it relates to a biodegradable chelating agent in the form of solid, aqueous-solution or slurry excellent in handleability and a detergent composition having excellent detergency and high in biodegradability which comprises the biodegradable chelating agent.
(2) Description of the Related Art
In general, chelating agents used in the form of solid are stored in the form of powder or flake in a bag or a hopper. Solid chelating agents gradually change to a hard mass due to the hardening property depending on accumulation condition and period and preservation condition and period. Therefore, the mass must be crushed just before the use and this is very inconvenient in handling.
Chelating agents used as aqueous solution or slurry are not needed to crush, but have serious problems such as deterioration in purity owing to decomposition in aqueous solution and coloration.
Generally, aminocarboxylic acid chelating agents are widely used as components of photographic bleaching agents, detergent compositions, detergent builders, heavy metal sequestering agents, stabilizers for peroxides and the like.
The detergent compositions are widely used for household cleaning of kitchenware, household cleaning of clothing, cleaning of dinnerware for business purpose, cleaning of plant, cleaning of clothing for business purpose, and the like. Furthermore, they are used as bleaching agents, descaling agents, metal sequestering agents, and the like together with additives suitable for the use.
Sodium tripolyphosphate which has hitherto been used as detergent builders is high in chelating performance. However, it contains phosphorus and causes eutrophication of rivers and lakes when it is discharged into environment. Thus, it is no longer used at present.
Zeolites which are used as detergent builders at present have disadvantages that they are low in chelating performance and have no biodegradability because they are inorganic materials. Furthermore, zeolites are insoluble in water and have a restriction in that they cannot be used for liquid detergents, especially clear liquid detergents. Moreover, zeolites have many problems such that they stick to inner wall of drainage pipes or settle at the bottom of rivers to cause formation of sludges. Therefore, the attempt is being made to reduce the amount of zeolites used and substitutes for zeolites which have sufficient chelating power and detergency have been desired, but such substitutes have not yet been obtained.
Of the aminocarboxylic acids which have been used as detergent builders, ethylenediaminetetraacetic acid (EDTA) has an excellent chelating power in a wide pH range, but is poor in biodegradability and is difficult to degrade by the usual waste water treatments which employ activated sludges. Furthermore, nitrilotriacetic acid (NTA) has a certain biodegradability, but is not preferred from the point of environmental health because it has been reported that NTA has teratogenicity and nitrilotriacetic acid-iron complex has carcinogenicity. Among other conventional aminocarboxylic acids, those which are excellent in chelating performance, but are low in biodegradability have the difficulty that they accumulate as injurious heavy metals in the environment when they are discharged into the environment. Various compounds have been studied as for the above-mentioned organic amino acids, but those which are excellent in chelating performance and biodegradability have not yet been reported at present.
The object of the present invention is to provide a biodegradable powdery chelating agent which does not harden into a mass during storage or a biodegradable chelating agent in the form of aqueous solution or slurry which does not undergo decomposition or discoloration during storage and to further provide a detergent composition comprising the chelating agent.
As a result of intensive research conducted by the inventors in an attempt to solve the above problems, it has been found that some chelating agents even in the form of solid can be handled easily without becoming hard under a specific condition, some chelating agents even in the form of aqueous solution or slurry can be handled stably and easily over a long period of time without undergoing decomposition or discoloration under a specific condition, and, further, a high detergency can be obtained by combining these biodegradable chelating agents with surface active agents and the like. Thus, the present invention has been accomplished.
That is, the chelating agent of the present invention is a chelating agent which comprises a compound of the following formula [1] and at least one compound selected from the group consisting of aspartic acid, maleic acid, acrylic acid, malic acid, glycine, glycolic acid, iminodiacetic acid, nitrilotriacetic acid, xcex1-alanine, xcex2-alanine, iminodipropionic acid, fumaric acid, an amino acid as a starting material for synthesis of the compound of the formula [1] (hereinafter referred to as xe2x80x9csynthetic starting amino acidxe2x80x9d), an intermediate amino acid produced in the synthesis reaction of the compound of the formula [1] (hereinafter referred to as xe2x80x9csynthetic intermediate amino acidxe2x80x9d), and salts thereof in an amount of 25% by weight or less based on the compound of the formula [1] and in the form of aqueous solution or slurry, or in an amount of 8% by weight or less based on the compound of the formula [1]: 
wherein R1 represents hydrogen or an unsubstituted or substituted hydrocarbon group of 1-10 carbon atoms and R2 represents hydrogen or an unsubstituted or substituted hydrocarbon group of 1-8 carbon atoms, with a proviso that R1 and R2 may form a ring together, the substituent which can be present in R1 and R2 is at least one member selected from the group consisting of xe2x80x94OH, xe2x80x94CO2M and xe2x80x94SO3M where M represents hydrogen or an alkali metal; X represents 
where R3 represents hydrogen or an unsubstituted or substituted hydrocarbon group of 1-8 carbon atoms, the substituent is at least one member selected from the group consisting of xe2x80x94OH, xe2x80x94CO2M and xe2x80x94SO3M, R4 represents at least one member selected from the group consisting of hydrogen, xe2x80x94CO2M and xe2x80x94SO3M, A1 and A2 each represent one member selected from the group consisting of hydrogen, CO2M and SO3M, A5 represents an alkylene group of 1-8 carbon atoms which may be of straight chain or branched chain or may form a ring, the alkylene group may contain in the chain an ether bond xe2x80x94Oxe2x80x94, an ester bond xe2x80x94COOxe2x80x94 or an amide bond xe2x80x94CONHxe2x80x94, M represents hydrogen or an alkali metal, and n represents an integer of 1-8; and Y represents at least one member selected from the group consisting of hydrogen, CO2M and SO3M.
Furthermore, the chelating agent of the present invention is a chelating agent in the form of aqueous solution or slurry which comprises a compound of the above formula [1] and at least one compound selected from the group consisting of aspartic acid, maleic acid, acrylic acid, malic acid, glycine, glycolic acid, iminodiacetic acid, nitrilotriacetic acid, xcex1-alanine, xcex2-alanine, iminodipropionic acid, fumaric acid, a synthetic starting amino acid, a synthetic intermediate amino acid, and salts thereof in an amount of 25% by weight or less based on the compound of the formula [1].
Moreover, the present invention relates to detergent compositions having excellent detergency and comprising the said biodegradable chelating agents.
As the monoamine compounds of the formula [1] where X is 
(wherein R3 and R4 are as defined above), mention may be made of, for example, aspartic acid-N-monoacetic acid (ASMA), aspartic acid-N,N-diacetic acid (ASDA), aspartic acid-N-monopropionic acid (ASMP), iminodisuccinic acid (IDA), N-(2-sulfomethyl)aspartic acid (SMAS), N-(2-sulfoethyl)aspartic acid (SEAS), glutamic acid-N,N-diacetic acid (GLDA), N-(2-sulfomethyl)glutamic acid (SMGL), N-(2-sulfoethyl)glutamic acid (SEGL), N-methyliminodiacetic acid (MIDA), xcex1-alanine-N,N-diacetic acid (xcex1-ALDA), xcex2-alanine-N,N-diacetic acid (xcex2-ALDA), serine-N,N-diacetic acid (SEDA), isoserine-N,N-diacetic acid (ISDA), phenylalanine-N,N-diacetic acid (PHDA), anthranilic acid-N,N-diacetic acid (ANDA), sulfanilic acid-N,N-diacetic acid (SLDA), taurine-N,N-diacetic acid (TUDA) and sulfomethyl-N,N-diacetic acid (SMDA) and alkali metal salts or ammonium salts thereof.
These compounds have asymmetric carbon and, hence, exist as optical isomers. From the viewpoint of biodegradability, preferred are (S)-aspartic acid-monoacetic acid, (S)-aspartic acid-N,N-diacetic acid, (S)-aspartic acid-monopropionic acid, (S,S)-iminodisuccinic acid, (S,R)-iminodisuccinic acid, (S)-2-sulfomethylaspartic acid, (S)-2-sulfoethylaspartic acid, (S)-glutamic acid-N,N-diacetic acid, (S)-2-sulfomethylglutamic acid, (S)-2-sulfoethylglutamic acid, (S)-xcex1-alanine-N,N-diacetic acid, (S)-serine-N,N-diacetic acid, and (S)-phenylalanine-N,N-diacetic acid and alkali metal salts or ammonium salts thereof.
As the diamine compounds represented by the formula [1] where X is 
(where A1, A2 and A5 are as defined above), mention may be made of, for example, ethylenediaminedisuccinic acid (EDDS), 1,3-propanediaminedisuccinic acid (13PDDS), ethylenediaminediglutaric acid (EDDG), 1,3-propanediaminediglutaric acid (13EDDG), 2-hydroxy-1,3-propanediaminedisuccinic acid (PDDS-OH) and 2-hydroxy-1,3-propanediaminediglutaric acid (PDDG-OH) and alkali metal salts or ammonium salts thereof.
These compounds have asymmetric carbon and, hence, there exist optical isomers. From the viewpoint of biodegradability, preferred are (S,S)-ethylenediaminedisuccinic acid, (S,S)-1,3-propanediaminedisuccinic acid, (S,S)-ethylenediaminediglutaric acid, (S,S)-1,3-propanediaminediglutaric acid, (S,S)-2-hydroxy-1,3-propanediaminedisuccinic acid and (S,S)-2-hydroxy-1,3-propanediaminediglutaric acid and alkali metal salts or ammonium salts thereof.
The monoamine compounds are generally obtained by a process which comprises subjecting the starting amino acid or sulfonic acid to addition reaction with hydrocyanic acid and formalin and hydrolyzing the resulting addition product under alkaline condition or a process which comprises subjecting amino acid or sulfonic acid to addition reaction with acrylonitrile or the like and hydrolyzing the resulting addition product under alkaline condition. Therefore, the desired monoamine chelating agents usually contain side reaction products as impurities in addition to the starting amino acid or sulfonic acid.
For example, in the synthesis of taurine-N,N-diacetic acid salt by adding hydrocyanic acid and formalin to taurine and, then, hydrolyzing the resulting addition reaction product, there are formed by-products such as glycolic acid, glycine, iminodiacetic acid, nitrilotriacetic acid, fumaric acid, xcex2-alanine and iminodipropionic acid in addition to unreacted taurine. In addition to these impurities, impurities such as malic acid and acrylic acid salts are sometimes detected depending on reaction conditions.
The diamine compounds are generally-produced by adding two molecules of maleic acid to one molecule of an alkylenediamine. In this case, the resulting desired diamine chelating agents usually contain, as impurities, unreacted maleic acid, reaction intermediate amino acid having only one molecule of maleic acid added and side reaction products thereof. For example, in the synthesis of an ethylenediaminedissucinic acid salt by adding two molecules of maleic acid to one molecule of ethylenediamine, there are seen by-products such as ethylenediaminemonosuccinic acid, fumaric acid and malic acid in addition to unreacted maleic acid.
Furthermore, for the production of the diamine compounds, there is a process according to which two molecules of the starting amino acid such as aspartic acid or glutamic acid are linked using dihaloethane, epichlorohydrin or the like. In this case, the resulting desired diaminopolycarboxylic acid chelating agents usually contain, as impurities, the starting amino acid, a reaction intermediate amino acid having only one molecule of the starting amino acid added and side reaction products thereof. For example, in the synthesis of (S,S)-ethylenediaminedissucinic acid by adding two molecules of (S)-aspartic acid to one molecule of dichloroethane and, then, subjecting the addition reaction product to precipitation with addition of a mineral acid, there are seen by-products such as (S)-N-2-chloroethylaspartic acid, (S)-N-2-hydroxyethylaspartic acid, (S,S)-N-2-hydroxyethylethylenediaminedisuccinic acid and fumaric acid in addition to unreacted (S)-aspartic acid.
In the present invention, the chelating agent is prepared so that the content of the above-mentioned impurity salts is 25% by weight or less, preferably 8% by weight or less based on the weight of the compound of the formula [1] in the form of a salt. When such condition is satisfied, especially when the content of the impurity salts is 8% by weight or less, the hardening of the resulting chelating agent is considerably inhibited even in the ordinary storing state. The total amount of the impurity salts is more preferably 3% by weight or less based on the weight of the compound of the formula [1], and further preferably 0.5% by weight or less for considerably inhibiting the hardening into a mass even under the severer storing conditions. When these conditions are satisfied, a powder inhibited from hardening into a mass can be obtained only by concentrating the reaction mixture for synthesis of the compound of the formula [1] (hereinafter referred to as merely xe2x80x9creaction mixturesxe2x80x9d) and, thereafter, subjecting the concentrated reaction mixture to spray drying and the like, but, in other cases, amount of the impurity salt can be reduced by carrying out the following purification.
As the surest purification means for the chelating agent, there is a method which comprises once subjecting the reaction mixture to precipitation with addition of a mineral acid such as sulfuric acid to isolate the chelating agent as a crystal of high purity and, then, redissolving the crystal in alkaline water. Further, when a solid crude chelating agent is purified, it is also effective to wash the chelating agent with an alcohol such as methanol to remove low-molecular impurities high in solubility.
In the present invention, when the impurities are in the form of acids, the chelating agents are also prepared in the same manner as in the case of the impurities being in the form of salts, namely, so that the content of these impurity acids is 25% by weight or less, preferably 8% by weight or less based on the compound of the formula [1]. When such condition is satisfied, especially when the content of the impurity acids is 8% by weight or less, the hardening of the resulting chelating agent is considerably inhibited even in the ordinary storing state. The total amount of the impurity acids is more preferably 3% by weight or less based on the compound of the formula [1], and further preferably 0.5% by weight or less for considerably inhibiting the hardening even under the severer storing conditions.
If the total content of the impurity acids (salts) cannot be permitted to meet with the above conditions by subjecting the chelating agent obtained by the above-mentioned reaction to only one precipitation operation with addition of an acid, the crude crystal may be purified by washing it with a large amount of water, by repeating recrystallization of the crude crystal, or by other methods.
The chelating agent purified to 25% by weight or less in the content of impurities by these methods can be easily returned to a powdery or flaky form even if the chelating agent sets during being stored or transported in the form of crystal or flake. Thus, the chelating agent can be stably and easily handled over a long period of time.
In the present invention, the chelating agent adjusted to contain the impurity salts in an amount of 25% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less based on the compound of the formula [1] can also be used in the form of an aqueous solution or slurry. When the chelating agent obtained by the above-mentioned reaction satisfies the above condition, the reaction mixture can be used as it is, but if the content of impurities exceeds the above range, an additional operation is needed for purification.
The chelating agent purified to 25% by weight or less in terms of the content of impurity salts by the above methods can be used as an aqueous solution or slurry containing at least 10% by weight of water, but from the points of preservativity and handleability, desirably, it is used as an aqueous solution or slurry of 5-80% by weight, preferably 20-50% in the salt concentration of chelating agent.
The materials of drums, tank lorries, storage tanks, stirrers and the like used for handling such as storing, transportation or mixing may be any of alloys, glass linings, synthetic resin linings and the like, and stainless steel is especially preferred.
The temperature at which the chelating agent of the present invention is handled is preferably 0-75xc2x0 C. in the case of the compound concentration being 5-40% by weight, 5-75xc2x0 C. in the case of the compound concentration being 40-50% by weight, and 10-75xc2x0 C. in the case of the compound concentration being 50-80% by weight.
Ordinarily, storage for about 3 years is possible under these conditions, and an aqueous solution or slurry of chelating agent not deteriorated in quality can be easily taken out and used as required.
The chelating agents obtained in this way constitute detergents having excellent detergency with addition of surface active agents and other additives.
These chelating agents are used normally in the form of alkali metal salts such as sodium salt and potassium salt, but can be used in the form of partially neutralized aqueous solution obtained by dissolving an acid form crystal isolated by precipitation with addition of an acid in an alkaline aqueous solution, in the form of the reaction mixture which is an alkaline aqueous solution, in the form of a solid salt obtained by concentrating the above aqueous solution, or in any other forms. If necessary, these can be adjusted to a pH suitable for the use. That is, the chelating agents of the present invention can be used in any forms of powder or flake inhibited from hardening into a mass and aqueous solution or slurry.
Next, the detergent composition of the present invention will be explained.
The detergent composition of the present invention contains the chelating agent of the present invention, especially, (S)-aspartic acid-N,N-diacetic acid, N-methyliminodiacetic acid and/or taurine-N,N-diacetic acid and, if necessary, a nonionic surface active agent, an anionic surface active agent, a silicate, a bleaching agent and/or a fatty acid salt.
The nonionic surface active agents usable in the present invention include, for example, ethoxylated nonylphenols, ethoxylated octylphenols, ethoxylated sorbitan fatty acid esters and propylene oxide adducts thereof, and are not especially limited. However, compounds obtained by random or block addition of 5-12, preferably 6-8 on an average of ethylene oxides and 0-12, preferably 2-5 on an average of propylene oxides per one molecule of an alcohol or phenol represented by the following formula [2], for example, ethoxylated primary aliphatic alcohols, ethoxylated secondary aliphatic alcohols and propylene oxide adducts thereof have especially high detergency. These nonionic surface active agents can be used each alone or in admixture of two or more.
Rxe2x80x94OHxe2x80x83xe2x80x83[2]
(R: an alkyl, alkenyl or alkylphenyl group of 8-24 carbon atoms).
The anionic surface active agents usable in the present invention include, for example, straight chain alkylbenzenesulfonic acid salts having alkyl group of 8-16 carbon atoms on an average, a-olefin sulfonic acid salts of 10-20 carbon atoms on an average, aliphatic lower alkyl sulfonic acid salts or salts of aliphatic sulfonation products which are represented by the following formula [3], alkylsulfuric acid salts of 10-20 carbon atoms on an average, alkyl ether sulfuric acid salts or alkenyl ether sulfuric acid salts having a straight chain or branched chain alkyl or alkenyl group of 10-20 carbon atoms on an average and having 0.5-8 mols on an average of ethylene oxide added thereto, and saturated or unsaturated fatty acid salts of 10-22 carbon atoms on an average. 
(R: an alkyl or alkenyl group of 8-20 carbon atoms, Y: an alkyl group of 1-3 carbon atoms or a counter ion, and Z: a counter ion).
The silicates usable in the present invention are silicates represented by the following formula [4] or aluminosilicates represented by the following formula [5], and these can be used each alone or in admixture of two or more at an optional ratio. Amount of the silicates is 0.5-80% by weight, preferably 5-40% by weight in the detergent compositions.
LMxe2x80x2SixO2(x+1).yH2Oxe2x80x83xe2x80x83[4]
(L represents an alkali metal, Mxe2x80x2 represents sodium or hydrogen, x represents a number of 1.9-4, and y represents a number of 0-20).
Naz[(AlO2)z(SiO2)y].H2Oxe2x80x83xe2x80x83[5]
(z represents a number of 6 or more, y represent a number which satisfies the ratio of z and y being 1.0-0.5, and x represents a number of 5-276).
The bleaching agents usable in the present invention include, for example, sodium percarbonate and sodium perborate. The amount of these bleaching agents is 0.5-60% by weight, preferably 1-40% by weight, more preferably 2-25% by weight in the detergent composition.
The fatty acid salts used in the present invention include, for example, alkali metal salts, alkaline earth metal salts, ammonium salts or unsubstituted or substituted amine salts, preferably alkali metal salts or alkaline earth metal salts, more preferably alkali metal salts of saturated or unsaturated fatty acids of 10-24 carbon atoms on an average. These fatty acid salts may also be used in admixture of two or more.
Examples of the fatty acid salts used in the present invention are alkali metal salts, alkaline earth metal salts, ammonium salts or unsubstituted or substituted amine salts, preferably alkali metal salts, alkaline earth metal salts, ammonium salts or unsubstituted or substituted amine salts, more preferably alkali metal salts of lauric acid, myristic acid, stearic acid and the like.
The detergent compositions of the present invention may further contain various additives such as stabilizers, alkali salts, enzymes, perfumes, surface active agents other than those of nonionic and anionic types, scale inhibitors, foaming agents and anti-foaming agents.
Detergent compositions of further higher performance can be obtained by using a plurality of the chelating agents in combination.
In some cases, chelating power cannot be sufficiently exhibited with use of one chelating agent depending on the pH employed, but excellent detergent compositions having detergency which is not influenced by the change of pH in the environment where they are used can be obtained by using a plurality of the chelating agents in admixture.
The chelating agents used in the detergent compositions of the present invention which are excellent in adaptability to pH are three of (S)-aspartic acid-N,N-diacetic acid, taurine-N,N-diacetic acid and N-methyliminodiacetic acid. Features of each of them will be explained below.
(S)-aspartic acid-N,N-diacetic acid can be used in the detergent compositions of the present invention excellent in adaptability to pH. Particularly, it imparts excellent performance in the neutral pH region, and, therefore, is preferred. It is especially great in chelate stability constant for calcium or the like among the above-mentioned three N,N-diacetic acid type chelating agents. Therefore, also in combination with carboxylic acid surface active agents such as sodium laurate, (S)-aspartic acid-N,N-diacetic acid chelates the objective metals firmly and is preferred.
It has been reported that the chelate stability constant for calcium of nitrilotriacetic acid is 6.4 and that of (S)-aspartic acid-N,N-diacetic acid is 5.8. However, there is a fact that as for the actual builder performance, (S)-aspartic acid-N,N-diacetic acid is superior to nitrilotriacetic acid. Since (S)-aspartic acid-N,N-diacetic acid is a monoamine chelating agent having four carboxyl groups, it can trap the objective metals such as calcium by quinquedentate coordination at the maximum. Therefore, when compared with nitrilotriacetic acid having three carboxyl groups and trapping the objective metals such as calcium by quadridentate coordination at the maximum, the chelating power of (S)-aspartic acid-N,N-diacetic acid is higher than that of nitrilotriacetic acid and exhibits conspicuously superior performance in the neutral region.
In combination with a sulfonic acid surface active agent such as sodium dodecylbenzenesulfonate, (S)-aspartic acid-N,N-diacetic acid has a Ca++ trapping power which is higher than that of nitrilotriacetic acid at a pH of 7-8 and equivalent to that of ethylenediaminetetraacetic acid.
When sodium laurate which is a carboxylic acid surface active agent is used in place of sodium dodecylbenzenesulfonate which is a sulfonic acid surface active agent, (S)-aspartic acid-N,N-diacetic acid retains a Ca++ trapping power of about 50% at a pH of 12. The Ca++ trapping power of (S)-aspartic acid-N,N-diacetic acid is inferior to that of ethylenediaminetetraacetic acid which retains a Ca++ trapping power of about 90% with the same substitution of the surface active agent as above, but is surprising in view of the fact that most of the known monoamine chelating agents completely lose the Ca++ trapping power in the presence of carboxylic acid surface active agents.
(S)-aspartic acid-N,N-diacetic acid is completely decomposed to inorganic materials in biodegradability tests such as 302A Modified SCAS Test described in OECD Guideline for Testing of Chemicals. It is completely decomposed in a certain period of time by activated sludges domesticated with waste water containing (S)-aspartic acid-N,N-diacetic acid.
Taurine-N,N-diacetic acid can be used in the detergent compositions of the present invention excellent in adaptability to pH and is especially preferred since it imparts an excellent performance in the weakly alkaline pH region.
As the chelate stability constant for calcium, a value of 4.2 has been reported for taurine-N,N-diacetic acid. However, on actual builder performance, there is a fact that taurine-N,N-diacetic acid is superior to nitrilotriacetic acid. When molecular structure of taurine-N,N-diacetic acid is viewed from the point of chelating performance, it comprises iminodiacetic acid portion which directly participates in trapping of the objective metal and sulfonic acid portion which participates in adaptation to pH of the objective metal trapping power. That is, it is considered that the sulfonic acid group of taurine-N,N-diacetic acid does not directly participate in trapping of the objective metal, but arranges the chemical environment so that molecules can readily exhibit the chelating power in more neutral side by the actions such as shifting of isoelectric point to the neutral side.
In combination with sulfonic acid surface active agents, taurine-N,N-diacetic acid has a Ca++ trapping power equal to that of ethylenediaminetetraacetic acid at a pH of 8 and superior to that of ethylenediaminetetraacetic acid at a pH of 8.5 or higher. This fact is surprising when compared with the fact that nitrilotriacetic acid which is a typical one of the same N,N-diacetic acid chelating agents exceeds ethylenediaminetetraacetic acid in Ca++ trapping power only when pH reaches 10, under the same conditions.
Taurine-N,N-diacetic acid is completely decomposed to inorganic materials in a short time in biodegradability tests such as 302A Modified SCAS Test mentioned above. It is completely decomposed in a short time by activated sludges domesticated with waste water containing tuarine-N,N-diacetic acid.
Methyliminodiacetic acid can be used in the detergent compositions of the present invention excellent in adaptability to pH and is especially preferred since it imparts an excellent performance in the alkaline pH region.
As the chelate stability constant for calcium, a value of 3.7 has been reported for methyliminodiacetic acid. However, on the actual builder performance, there is a fact that methyliminodiacetic acid exceeds nitrilotriacetic acid. When molecular structure of methyliminodiacetic acid is viewed from the point of chelating performance, it is considered that the chelate stability constant for calcium increases than that of simple iminodiacetic acid due to the conversion of the amino group to tertiary amino group by the introduction of methyl group and the Ca++ trapping power per weight increases due to its small molecular weight.
In combination with sulfonic acid surface active agents, methyliminodiacetic acid is far greater in the Ca++ trapping power than ethylenediaminetetraacetic acid at a pH of at least 10 and, besides, it shows a surprising performance which further exceeds the performance of nitrilotriacetic acid which has been considered to have excellent performance under the same conditions.
Methylimino-N,N-diacetic acid is completely decomposed to inorganic materials in a short time in biodegradability tests such as 301C Modified MITI Test (1) described in OECD Guideline for Testing of Chemicals. Methyliminodiacetic acid is readily decomposed by microorganisms living in environmental water such as rivers, lakes, and general sewage without subjecting to activated sludge treatment and the like.
(S)-aspartic acid-N-monoacetic acid and (S)-aspartic acid-N-monopropionic acid are biodegradable builders substitutable for methyliminodiacetic acid, but although they show excellent builder performance at a pH of 10 or higher, they are inferior to methyliminodiacetic acid in Ca++ trapping power per weight, and, hence, they must be used in a large amount. (S)-aspartic acid-N-monoacetic acid and (S)-aspartic acid-N-monopropionic acid are completely converted to inorganic materials in a short time in biodegradability tests such as 301C Modified MITI Test mentioned above. They are readily decomposed by microorganisms living in environmental water such as rivers, lakes and general sewage without subjecting to activated sludge treatment and the like.
In the above, (S)-aspartic acid-N,N-diacetic acid, taurine-N,N-diacetic acid and methyliminodiacetic acid are explained on their features as biodegradable builders. The detergent compositions containing simultaneously at least two of them as builder components can exhibit excellent performances in a wide pH condition. That is, by properly containing these builder components, performances equal to or higher than those of ethylenediaminetetraacetic acid which has hitherto been preferably used as an excellent builder can be obtained in a wide pH condition of from neutral region to alkaline region. Furthermore, it is also possible to bring out especially excellent performances under the conditions of a specific pH and a specific surface active agent by increasing the content of a specific biodegradable builder component.
In the uses such as pulp and clothing, hydrogen peroxide or organic peroxides are added for the purpose of bleaching, and builders have the function to protect these peroxides from decomposition action catalyzed by heavy metals such as iron.
In the field of food processing industry, detergent compositions containing only the builder component as a main ingredient and containing no surface active agent are sometimes used for removal of calcium carbonate, calcium oxalate and the like in washing of beer bottles, dinnerwares and plants.
The detergent compositions of the present invention may contain, as buffers, stabilizers and resticking inhibitors, general auxiliary additives, salts of silicic acid, crystalline alluminosilicic acid, laminar silicic acid and the like, salts of amino acids such as glycine, xcex2-alanine, taurine, aspartic acid and glutamic acid, salts of polymers such as polyacrylic acid, polymaleic acid, polyaconitic acid, polyacetalcarboxylic acid, polyvinyl pyrrolidone, carboxymethylcellulose and polyethylene glycol, salts of organic acids such as citric acid, malic acid, fumaric acid, succinic acid, gluconic acid and tartaric acid, enzymes such as protease, lipase and cellulase, and salts of p-toluenesulfonic acid and sulfosuccinic acid.
There can be further added caking inhibitors such as calcium silicate, peroxide stabilizers such as magnesium silicate, antioxidants such as t-butyl-hydroxytoluene, fluorescent paints, perfumes and others. These are not limited and may be added depending on the uses.
The present invention does not preclude to use, in combination with the above builders, salts of tripolyphosphoric acid, pyrophosphoric acid and the like, salts of diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid and the like, and others as builders. However, from the points of safety and diminishment of environmental load, it is desirable to avoid use of these conventional builders.
Next, use conditions and ratio of the components of the detergent compositions according to the present invention will be explained in detail.
In order to obtain a performance equal to or higher than that of ethylenediaminetetraacetic acid which is an excellent builder under wide use conditions, it is desired to use simultaneously at least two biodegradable builders among the three builders of (S)-aspartic acid-N,N-diacetic acid, taurine-N,N-diacetic acid and methyliminodiacetic acid. It is preferred to use (S)-aspartic acid-N,N-diacetic acid in an amount of 5-97% by weight, preferably 40-95% by weight in terms of acid, taurine-N,N-diacetic acid in an amount of 0-97% by weight, preferably 40-90% by weight in terms of acid, and methyliminodiacetic acid in an amount of 0-97% by weight, preferably 30-70% by weight in terms of acid. Desirably, the total amount of the builders is 6-810% by weight, preferably 20-240% by weight, more preferably 80-120% by weight in terms of acid based on the surface active agent component.
In case of employing such compositional ratio of the biodegradable builders, a builder performance per weight in terms of acid equal to or higher than that of ethylenediaminetetraacetic acid or nitrilotriacetic acid is developed in the pH range of 6-13 in combination with surface active agents such as of sulfonic acid type excellent in dispersibility and in the pH range of 7-12 in combination with surface active agents such as of carboxylic acid type poor in dispersibility. The builder performance here includes not only the Ca++ trapping power, but also performances such as dispersing ability for scale or heavy metals, pH buffering ability, inhibition of dirt from resticking, inhibition of liquid detergent from setting and shape retention of solid detergent, and the builders according to the present invention also exceed nitrilotriacetic acid in these performances and performances not inferior to those of ethylenediaminetetraacetic acid and tripolyphosphoric acid can be obtained.
When conditions such as pH and surface active agent used are previously known for some uses, it is advantageous to prepare the detergent compositions with compositional ratio of the biodegradable builders suitable for these use conditions.
In many cases, household neutral detergents for kitchen and clothing are used at a pH of about 6.5-8.5 in combination with surface active agents such as dodecylbenzenesulfonates, lauryl alcohol sulfate esters and polyethylene glycol. In these uses, it is suitable to use (S)-aspartic acid-N,N-diacetic acid in an amount of 20-97% by weight, preferably 50-95% by weight in terms of acid, taurine-N,N-diacetic acid in an amount of 5-90% by weight, preferably 50-80% by weight in terms of acid, and methyliminodiacetic acid in an amount of 0-20% by weight, preferably 10-15% by weight in terms of acid on the basis of the builder composition.
Industrial detergents for cleaning of clothing, dinnerwares, plants, bottles and others are used at a pH in a wide range from neutral to strongly alkaline conditions. Especially, in the uses under alkaline condition of pH 9-13, it is suitable to use (S)-aspartic acid-N,N-diacetic acid in an amount of 0-90% by weight, preferably 20-50% by weight in terms of acid, taurine-N,N-diacetic acid in an amount of 5-90% by weight, preferably 50-80% by weight in terms of acid, and methyliminodiacetic acid in an amount of 20-97% by weight, preferably 60-90% by weight in terms of acid on the basis of the builder composition.
However, even in the uses of industrial detergents under alkaline condition of pH 9-13, when surface active agents such as laurates inferior in dispersibility are used, it is favorable to use (S)-aspartic acid-N,N-diacetic acid in an amount of 20-95% by weight, preferably 50-90% by weight in terms of acid, taurine-N,N-diacetic acid in an amount of 5-90% by weight, preferably 50-80% by weight in terms of acid, and methyliminodiacetic acid in an amount of 0-20% by weight, preferably 10-15% by weight in terms of acid on the basis of the builder composition.
Furthermore, in any uses, the whole or a part of methyliminodiacetic acid which is a biodegradable builder component in the detergent composition of the present invention can be replaced with one or both of (S)-aspartic acid-N-monoacetic acid and (S)-aspartic acid-N-monopropionic acid. When (S)-aspartic acid-N-monoacetic acid is used, it is suitable to use it in an amount of 80-350% by weight, preferably 150-320% by weight in terms of acid based on the methyliminodiacetic acid. When (S)-aspartic acid-N-monopropionic acid is used, it is suitable to use it in an amount of 120-560% by weight, preferably 240-420% by weight in terms of acid based on the methyliminodiacetic acid.
The detergent composition of the present invention can also be prepared as a liquid detergent or powder detergent of high concentration by mixing, at a predetermined ratio, the chelating agent with surface active agents and others which are the constituting components and this can be diluted to a desired concentration with water at the time of use. Alternatively, these components can be added to a diluting water at a predetermined ratio.